The present invention generally relates to an actuator arm adapted to drive a head in a disk apparatus, and more particularly, to a latch mechanism adapted to hold the actuator arm in a predetermined position during non-operation of the disk apparatus.
A disk apparatus for recording and reproducing information to or from a disk medium must to avoid wear which results from contact between the head slider and the disk surface. Therefore, a contact-start-stop (CSS) system is employed in which, during non-operation of the disk apparatus, the head is in contact with the disk surface, and during operation of the disk apparatus, namely, during recording or reproducing operations, the head floats above the rotating disk surface.
In a disk apparatus employing the CSS system, the head slider includes a head element to record or reproduce information to or from a disk which floats away from the rotating disk surface during operation of the disk drive by receiving air flow generated by rotation of the disk. When information is recorded or reproduced, the head slider moves while floating above the rotating disk surface and is then placed over a predetermined track of the disk. When the disk apparatus is in the non-operating condition, the head slider is placed within the CSS zone provided on the disk surface. Moreover, when the disk apparatus is in the non-operating condition, since the disk is not rotating, air flow for floating the head slider is not generated and the head slider is in contact with the CSS zone.
If the disk apparatus receives a shock when the head slider is in contact with the CSS zone, the head slider may move to the data zone and cause damage, namely, a destruction of data or a disabling of the data reading or writing operation. In recent years, with reduction of size, such a disk apparatus has been used in portable devices such as note-sized personal computers. Such a disk apparatus is often placed in a condition where it may easily receive an external shock. Therefore, high durability against shock is one of the performance characteristics required for a disk apparatus.
Therefore, a latch mechanism has been provided so that the actuator is fixed in the stop position when the disk apparatus is in the non-operating condition. By providing the latch mechanism, if the disk apparatus receives a certain degree of shock, the head slider does not move to the data zone and thereby the disk and data can be protected.
FIGS. 1(a) and 1(b) illustrate a structure of the latch mechanism of the related art. A voice coil 51 is mounted at the rear end surface of an actuator 22 which supports a head slider 4,. The voice coil 51 is placed within magnetic fields generated by an upper permanent magnet 54 provided at the lower surface of an upper yoke 52, and a lower permanent magnet 55 provided at the upper surface of lower yoke 53. A voice coil motor (VCM) 23 which rotates the actuator 22 includes the voice coil 51, upper and lower yokes 52, 53 and permanent magnets 54, 55 or the like.
A latch magnet 11 is provided in the area outside the magnetic field of the rear end surface of the actuator 22. Moreover, opposing dowels 12 are provided which sandwich the plane of motion of the latch magnet 11. The dowels are located at the lower surface of upper yoke 52 and at the upper surface of the lower yoke 53. The dowels 12 are generally formed by pressing the yokes 52, 53.
According to this structure, when the head slider 4 stops in a CSS zone 31 of a disk 1, the latch magnet 11 is proximal to the dowels 12 and magnetic force attracts the latch magnet 11 toward the dowels 12. As a result, a counterclockwise torque is generated in the actuator 22 and thereby the actuator 22 is energized or biased in the counterclockwise direction. Therefore, when the head slider 4 receives a shock when it is in contact with the CSS zone 31, it is prevented from moving to data zone 32.
In order to realize a highly reliable latch mechanism, the actuator 22 must be energized or biased toward the CSS zone 31 by an intensive torque. In the latch mechanism illustrated in FIG. 1, the magnetic force of latch magnet 11 must be intensified to attain a strong latch force. However, when the magnetic force of the latch magnet 11 is raised, a significant attracting force is generated between the dowels 12 and the latch magnet 11 even during seek operations, resulting in an influence on the seek control. As a result, the seek control becomes difficult and the processing speed is decreased. Moreover, when an intensified magnetic force of the latch magnet 11 is required, it also requires enlargement of the latch magnet 11. Since the latch magnet 11 illustrated in FIG. 1 is provided at the far end of the rotating shaft of the actuator 22, enlargement of latch magnet 11 requires a large rotating inertia of the actuator 22 to release the latch. Thereby, the load on VCM 23 becomes large and power consumption also becomes large.
As a solution to the problems explained above, a latch mechanism utilizing a solenoid and a mechanical latch mechanism utilizing air pressure generated by rotation of the disk medium have been proposed, but these mechanisms require the addition of expensive parts, thereby increasing cost.
It is therefore a first object of the present invention to improve the shock resistance of a disk apparatus.
It is a second object of the present invention to provide a disk apparatus which assures high speed operation.
It is a third object of the present invention to provide a low cost disk apparatus.
It is a fourth object of the present invention to provide a latch mechanism having a simplified structure.
It is a fifth object of the present invention to provide a latch mechanism having a large latching force.
In a latch mechanism used for a disk apparatus of the present invention, a latch force is obtained from a latch magnet attached to an actuator. The latch magnet passes through a magnetic field generated by two permanent magnets of a voice coil motor (VCM), with a rotating or swinging shaft of the actuator defining a center of rotation. According to this structure, a magnetic force in the rotating direction of the actuator can be generated between the latch magnet and the permanent magnets of the VCM when the actuator is in certain locations. The magnetic force working on the permanent magnets is higher than the magnetic force working between the metal piece and magnet of the related art. Therefore, an intensive latch force can be obtained from this magnetic force to improve the shock resistance of the disk apparatus. In addition, the latch mechanism has a simplified structure which does not require additional parts and therefore a low cost disk apparatus can be realized. Moreover, the latch magnet can be located proximal to the rotating shaft of the actuator, thereby decreasing the rotational inertia of the actuator. Accordingly, the load required for the VCM drive the actuator is alleviated to realize reduction of power consumption and high speed seeking.
Moreover, when the direction of the magnetic flux of the latch magnet is parallel to the direction of the magnetic flux generated by the permanent magnets of the VCM, and the head slider is resting on the CSS zone, it is preferable that the latch magnet be placed at least partially outside of the magnetic field of the permanent magnets. According to this structure, when the disk is in the non-operating condition and a latching of the actuator is required, a magnetic force in the direction of rotation of the actuator is generated between the latch magnet and the permanent magnets, and an intensive latch force can be obtained from this lateral magnetic force.
Moreover, when the head slider is located at a position furthest from the CSS zone in the movable range of the actuator, it is preferable for the latch magnet to be placed in the magnetic field of the permanent magnets. According to this structure, a magnetic force is not generated between the permanent magnets and the latch magnet during the seek operation, and therefore such a magnetic force does not influence the seek control. Therefore, high speed seek control may be realized.